Bacteria belonging to the genus Bifidobacterium are obligate anaerobes and are weak in an aerobic condition. In fermentation products, it is difficult to handle in view of proliferation during the production and viability under storing. In order to obtain physiological effects (intestinal function controlling effect or the like) of the bacteria belonging to the genus Bifidobacterium, they must reach the intestine in a viable form as much as possible. It is thought to be an important factor in the production of the fermented foods of this type to increase in the viability of bacteria in the fermented foods and an arriving rate of bacteria to the intestine after meal.
As a result of improvement in bacterial strains by various methods, strains improved in proliferation and viability have recently been prepared. In addition, an improvement in viability is performed also in fermented foods by an improvement of production process and addition of various agents for improving the viability, such as N-acetyl glucosamine, pantothenic acid, pantethine, pantetheine, peptides and lactulose.
However, in the production site of the fermented foods, it is difficult to pack all fermented products of Bifidobacterium bacteria on the same day from the viewpoint of production cost and working ability, and at present, semimanufactured products products admixed with other additives or the like are stored in the aerobic storage tank for several days. In order to stably supply a product with a superior viability satisfying a quality standard for maintaining high viable count even under such aerobic circumstance, further improvement in the viability is required.
Under such circumstance, viable bacteria living in severe conditions such as aerobic condition or addition of acid did not always exhibit increased viability. As a result, it was extremely difficult to obtain a bacterial strain having more superior viability as compared with known bacteria. Further, even by the improvement of the production process and the addition of various viability improving agents, it was difficult to maintain the viability of bacteria in the fermented foods which were aerobically stored in the production site, at a sufficiently high level even after shipment of the products.
Consequently, an object of the present invention is to provide a bacterium belonging to the genus Bifidobacterium having a high viable count and good viability, even after storing for desired term until packing into a vessel and shipping to the market after fermentation of the bacterium, and fermented foods produced by using the same.